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US 4,230,184 AGranted
Sulfur extraction method
AssigneeShell Oil Company
InventorGeorge C. Blytas
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AssigneeShell Oil Company
InventorGeorge C. Blytas
Estimating the term…
Circulating oil used for removal of sulfur in sour gas wells is contacted with an aqueous solution of a lower polysulfide of an alkali metal or ammonia to form a higher polysulfide of the alkali metal or ammonia, and the oil is separated from the higher polysulfide. The higher polysulfide is converted to lower polysulfide by precipitating part of the sulfur contained therein, and the lower polysulfide is recycled for oil desulfurization.
A process for extracting sulfur from a mineral oil-sulfur solution wherein the mineral oil is at least partly in the form of an emulsion with a minor quantity of water comprising treating said solution by adding an oil/water emulsion-breaking surfactant thereto, contacting the treated solution with an aqueous solution of a lower polysulfide of an alkali metal or ammonia to form a higher polysulfide of said alkali metal or ammonia, and separating the mineral oil from the higher polysulfide.
A process for extracting sulfur from a mineral oil-sulfur solution comprising forming the solution by circulating the oil to remove sulfur deposits from a riser in a natural gas well, the oil having a viscosity lower than 200 centistokes at 122.degree. F., and lower than 20 centistokes at 212.degree. F., contacting said solution with an aqueous solution of a lower polysulfide of an alkali metal or ammonia to form a higher polysulfide of said alkali metal or ammonia, and separating the mineral oil from the higher polysulfide.
A process for extracting sulfur from a mineral oil-sulfur solution comprising contacting said solution with an aqueous solution of a lower polysulfide of an alkali metal or ammonia to form a higher polysulfide of said alkali metal or ammonia, separating the mineral oil from the higher polysulfide and regenerating the lower polysulfide from the higher polysulfide by absorption of H.sub.2 S, thereby reducing the pH of the polysulfide and causing precipitation of sulfur.
A process for extracting sulfur from a mineral oil-sulfur solution comprising contacting said solution with an aqueous solution of a lower polysulfide of an alkali metal or ammonia to form a higher polysulfide of said alkali metal or ammonia, separating the mineral oil from the higher polysulfide and producing the lower polysulfide by recycling the higher polysulfide to be admixed with hydrosulfide produced by passing sour gas containing at least 20% v H.sub.2 S through an alkali hydroxide solution.
A countercurrent process for extracting sulfur from a mineral oil-sulfur solution comprising contacting the solution with an aqueous solution of a lower polysulfide of an alkali metal or ammonia to form a higher polysulfide of said alkali metal or ammonia, separating the mineral oil and remaining sulfur from the higher polysulfide, then contacting the mineral oil and remaining sulfur with a hydrosulfide to form a lower polysulfide, separating the mineral oil from the lower polysulfide, and recycling the lower polysulfide to be contacted with the mineral oil-sulfur solution.
Dependencies are inferred from the claim text.
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No related US applications are recorded in the indexed filing history.
Characterised by the solvent used: inorganic compounds only
Of solutions which are liquid: counter-current multistage extraction towers in a vertical or sloping position
Of solutions which are liquid: flow sheets
Preparation of sulfur; Purification: from non-gaseous sulfides or materials containing such sulfides, e.g. ores
Term ended 1 Dec 1998 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
In deep sour gas wells, oil may be pumped down the annulus between the well casing and the production tubing in order to prevent sulfur deposition, and to carry oil-soluble corrosion inhibitors. Alternatively, oil may be injected into surface gathering lines to prevent sulfur deposition. The oil flows back up through the production tubing along with the produced gasses, is separated from the gasses at the gas plant, and recycled back to the wells (U.S. Pat. No. 3,393,733). As the oil circulates, it absorbs a small amount of elemental sulfur which is produced by the wells. Since the oil is recirculated, there is a continuous increase in sulfur concentration. In order to operate over a long period of time, it is necessary to control the sulfur concentration by removing it from the well as fast as it is added. Use of a sulfide solution of an alkali metal or ammonia to extract sulfur from a mineral oil-sulfur solution is disclosed in U.S. Pat. 3,474,028, and the present invention represents an improvement over the process of this patent.
The primary purpose of this invention resides in extracting sulfur from an oil, particularly a circulating oil used to prevent sulfur deposition in deep sour gas wells.
The above purpose has been achieved by extracting sulfur from circulating oil used to prevent sulfur deposition in deep sour gas wells with aqueous solutions of a lower polysulfide of an alkali metal or ammonia.
FIGS. 1 and 2 schematically depict the sulfur-extraction process of the invention.
FIGS. 3 and 4 show techniques for regeneration of lower polysulfides.
In accordance with FIG. 1, oil containing sulfur and emulsified water (production water can be up to 30-40% volume of the oil as it comes from a gas well) is taken from a wash tank, storage, a sour gas well, or some other point, and pumped through an emulsion-cracking and dewatering station 1 wherein it is mixed with a cracking agent 2 so that water may be removed, and then through a sulfur removal station 3 wherein it is mixed with an aqueous lower polysulfide stream 4. The oil and aqueous polysulfide phases which are formed separate in a settling station 5 (the cracking agent 2 also serves to separate the aqueous polysulfide), and the oil phase 6 may be washed with water and/or returned to the well, or some other point, through gathering lines, and a higher polysulfide phase 7 is removed for disposal or regeneration.
Stations 1 and 2 may comprise static end line mixing sections which are used to provide turbulent mixing of the oil and emulsion-cracking agent and/or polysulfide. The mixing sections may consist of mixing elements inside pipe sections, pipes packed with Raschig rings or similar packing, or simply pipe sections of varying diameter. Alternatively, mixing may be carried out in tanks or other suitable vessels using a powered stirrer.
The polysulfide and oil phases separate in station 5 with the polysulfide going to the bottom, in the case of an alkali metal sulfide, and to the top in the case of ammonium polysulfide. Station 5 may be a tank sized to allow at least several hours residence time for the oil and an equal volume of the polysulfide phase. Flow into the tank can be through a spreader, near the bottom, flow out can be by gravity.